Electrical safety block

ABSTRACT

A device adapted for attachment to one of the male prongs of an electrical plug to prevent insertion of the plug into an electrical receptacle.

United States Patent Liburdi Dec. 25, 1973 [54] ELECTRICAL SAFETY BLOCK 595,196 12/1897 Newman et al. 24 125 R 2,537,370 l/l95l Park s .1 339/195 R [76] Inventor: Frank f 4629 Burs-sens 1,517,017 11 1924 Rom 339/198 E x warren, Mlch- 48092 3,414,866 12/1968 Norden. 339/198 E x 3,710,287 1/1972 Eckert 339/l95 R [22] June 1972 3,662,296 5 1970 Newman... 339 36 [21] Appl. No.: 260,908 3,123,424 3/1964 Williams 339/195 .11

Primary Examiner-Marvin A. Champion 33 37 339195 R g h 13/52 Assistant ExaminerTerrell P. Lewls 58 Field of Search 339/36, 37, 82, 195, "auke [57] ABSTRACT [56] References Clted A device adapted for attachment to one of the male UNITED STATES PATENTS prongs of an electrical plug to prevent insertion of the 812,287 2/1906 Nagel 339/246 X plug into an electrical receptacle.

3 Claims, 3 Drawing Figures ELECTRICAL SAFETY BLOCK BACKGROUND OF THE INVENTION l. Field of the Invention This invention relates to male electrical plugs and more particularly to means to be attached to one of the prongs of such plugs to prevent insertion of the plug into an electrical receptacle.

2. Description of the Prior Art Devices have been heretofore provided for attachment to the prong of an electrical male plug for preventing unauthorized use of electrical appliances, tools and the like. These devices have usually been in the form of means adapted to be clamped over both male prongs of the plug and locked into place by a padlock or the like as shown in U.S. Pat. No. 3,345,600 issued to L. F. Scherer on Oct. 3, I967.

While such locks are adequate to prevent unauthorized use of the appliance or tool, they are unduly complicated and thus unnecessarily expensive to manufacture. Also each lock requires a separate key which must be retained and located each time the appliance or tool is to be used.

SUMMARY OF THE INVENTION The present invention provides a relatively simple lock for the prong of a male plug. The lock is designed to prevent small children from inserting the plug into a receptacle and thus being injured by the electrical tool or appliance. The lock comprises a block member fashioned to fit over one of the male prongs and a buttonhead Allen screw or similar means for insertion through the aperture which is conventionally provided at the end of the male prongs and into a threaded aperture in the block membemThe Allen screw provides the means for securely clamping the block member to one of the male prongs.

As long as the block member is attached to the male prong it will prevent insertion of the male plug into an electrical receptacle. Removal of the block member can be accomplished by an Allen wrench so that no key is necessary. Loosening of the screw will not ordinarily be accomplished by small cildren.

BRIEF DESCRIPTION OF THE DRAWINGS The description herein refers to the accompanying drawings wherein like reference characters refer to like parts throughout the several views, and in which:

FIG. I is a perspective view illustrating the safety block of the present invention in place;

FIG. 2 is an exploded perspective view similar to FIG. I but illustrating the safety block removed from the prong of the male electrical plug; and

FIG. 3 is a cross-sectional view taken substantially on line 3-3 of FIG. I.

DESCRIPTION OF A PREFERRED EMBODIMENT A male electrical plug is illustrated in FIGS. 1 and 2 as including a pair of prongs 12, each having an aperture 14 near its free end. This is conventional construction for such plugs.

A substantially rectangular block 16 is formed with a rectangular recess 18 along one side as best seen in FIGS. 2 and 3. The recess 18 is formed to accommodate either of the prongs 12 in the manner illustrated in FIGS. 1 and 3. A threaded aperture 20 formed in the block 16 is positioned to align with the aperture 14, as shown in FIG. 3, and receives a screw 22 which extends through the aperture 14 and which can be tightened into the aperture 20 formed in the block 16. In this way the block 16 can be securely clamped to either of the prongs 12 to prevent insertion of the prongs 12 into a conventional electrical receptacle (not shown).

The male plug 10 is adapted to be attached to an electrical appliance or tool (not shown) and the appliance or tool cannot be operated as long as the safety block 16 is in place.

The screw 22 is preferably a buttonhead Allen screw or the like so that it cannot be loosened by an ordinary screwdriver. This will discourage removal and will even prevent removal by small children, while at the same time will not present an undue burden on one having a use for the appliance or tool. It will not be necessary to find the right key for removing the safety block each time the tool or appliance is to be used.

It is apparent that I have described a simple and economical device for attachment to the prongs of a male plug to thereby prevent unauthorized use of an electrical appliance or tool. The device does not require a key for removal so that the problems encountered with the key-type locks are avoided.

It is also apparent that although I have described but a single embodiment of my invention many changes and modifications can be made therein without departing from the spirit of the invention or the scope of the appended claims.

I claim:

I. In combination with a male electrical plug for an electrical tool or the like said male plug having a pair of prongs, each of said prongs having an aperture, a lock for preventing insertion of said prongs into a female plug, said lock comprising a block and means securing said block to one of said prongs, said means comprising a screw extending through the aperture of said prong and into said block.

2. The combination as defined in claim 1 and in which said block member is rectangular and includes a recess for receiving one of said prongs.

3. The combination as defined in claim 1 and in which said screw means comprises a buttonhead Allen screw.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 913 Dated pecember 25, 1973 P Inventor(s) Frank Liburdi It is certified that error. appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 17, after "male", insert -electrical--;

line 28, after "block", insert -l6,-

line 49, after "through", delete "the" and insert Signed and sealed this' 2 nd day of July 1974.

(SEAL) Attest:

EDWARD M. FLETCHER,JR. C.MARSHALL DANN Attesting Offieer v Commissioner of Patents I FORM P0-105O (10-69) USCOMM-DC 60376-1 69 U,S. GOVERNMENT PRINTING OFFICE: I969 0-366-334 

1. In combination with a male electrical plug for an electrical tool or the like said male plug having a pair of prongs, each of said prongs having an aperture, a lock for preventing insertion of said prongs into a female plug, said lock comprising a block and means securing said block to one of said prongs, said means comprising a screw extending through the aperture of said prong and into said block.
 2. The combination as defined in claim 1 and in which said block member is rectangular and includes a recess for receiving one of said prongs.
 3. The combination as defined in claim 1 and in which said screw means comprises a buttonhead Allen screw. 